The feeble nucleofugality of a nitronate leaving group and its enhancement by ring strain
作者:Pier Paolo Piras、Patsy J. Thomas、Charles J. M. Stirling
DOI:10.1039/c39820000658
日期:——
The rank of a nitronate ion in activated alkene-forming elimination is low (+2.6); incorporation of the leaving goup in a cyclopropane accelerates elimination so much that the (ElcB)R–(ElcB)I borderline is traversed but the retro-Thorpe–Ingold effect nevertheless operates.
在形成活化烯烃的消除中,亚硝酸根离子的等级较低(+2.6);在环丙烷中加入离去基团可加快消除速度,以至于可以越过(E l cB)R –(E l cB)I边界,但仍会产生逆向索普-英戈尔德(Thorpe-Ingold)效应。
New synthetic methods. Conjugate addition of alkyl groups to electron deficient olefins with nitroalkanes as alkyl anion equivalents
The N,N-diethylpropylamine supported on amorphous silica (KG-60-NEt2) catalyses the formation of carbon-carbon bonds by nitroalkanes through both the nitroaldol (Henry) and Michael reactions. The catalyst shows general utility with a variety of electrophilic acceptors. Moreover, the catalyst can be reused for two further cycles without loss of the activity. (C) 2003 Published by Elsevier Science Ltd.